Even when an Ubuntu system appears to be idle, many system processes will be running silently in the background to keep the operating system functioning. Each time you execute a command or launch an app, user processes are started which will run until the associated task is completed.
To obtain a list of active user processes you are currently running within the context of a single terminal or command-prompt session use the ps command as follows:
$ ps
PID TTY TIME CMD
10395 pts/1 00:00:00 bash
13218 pts/1 00:00:00 ps
The output from the ps command shows that there are currently two user processes running within the context of the current terminal window or command prompt session, the bash shell into which the command was entered, and the ps command itself.
To list all of the active processes running for the current user, use the ps command with the -a flag. This will list all running processes that are associated...